A compact disc is included herewith and incorporated by reference herein having thereon a computer program listing appendix in the ASCII uncompressed text format with ASCII carriage return, ASCII line feed and all control codes defined in ASCII, having computer compatibility with IBM PC/XT/AT or compatibles, having operating system compatibility with MS-Windows and including files source_code_1617_Hxe2x80x2.txt and source_code_1617_Hxe2x80x3.txt of 13,747 bytes and 10,462 bytes, respectively, both created on Sep. 25, 2002.
1. Field of the Invention
The present invention is directed to a rate 16/17 coding system for encoding or decoding data while minimizing propagation of any errors introduced after the encoding and before the decoding and while assuring certain bit properties of words encoded by the coding system.
2. Description of the Related Art
To minimize errors introduced during the conveyance of data, and to assure certain bit properties of the data when it is in encoded form for conveyance, systems often encode data before it is filtered or conveyed between two points. Encoding typically involves transforming the data and introducing additional information to the data, where the additional information can be used to recover from or minimize the effect of discrepancies that can be introduced during conveyance.
A coding scheme (or code) may be measured by two opposing qualities. A first quality of a coding scheme is the efficiency or rate of the code, which is the amount of input data to be encoded, in proportion to the amount of the input data plus added coding information. For example, if a code adds one coding bit to a 16-bit input word, thus producing a 17-bit codeword, then the rate of the code is 16/17. A high coding rate naturally leads to an efficient rate of conveying the input data, because less total information must be conveyed per unit of input data that is conveyed. A second quality of a coding scheme is the degree to which the added coding information facilitates recovery from or minimization of errors introduced during conveyance. There is a tension between these two coding qualities. Higher error recovery rates (desirable) generally require less efficient coding rates (undesirable). More efficient coding rates (desirable) generally lead to lower error recovery rates (undesirable). Furthermore, Low error recovery or high error propagation can also require a more complex outer error correction code. What is needed is a coding scheme with a low error propagation rate and an efficient coding rate that guarantees various benefits relating to the bit make-up of a codeword without requiring a complex outer error correction code.
It is an aspect of the present invention to provide a rate 16/17 coding system that exhibits various combinations of code properties. In a first embodiment of the rate 16/17 code, if a codeword Hxe2x80x2 is (H1xe2x80x2 H2xe2x80x2), where H1xe2x80x2 represents the first 8 bits of the Hxe2x80x2 codeword, and H2xe2x80x2 represents the last 9 bits of the Hxe2x80x2 codeword, then:
1) each codeword Hxe2x80x2 has at least 7 bits with a value of 1;
2) H1xe2x80x2 has at least 3 bits with a value of 1;
3) H2xe2x80x2 has at least 3 bits with a value of 1;
4) H1xe2x80x2 has at least 1 odd-coordinate bit with a value of 1, and at least 1 even-coordinate bit with a value of 1;
5) H2xe2x80x2 has at least 1 odd-coordinate bit with a value of 1, and at least 1 even-coordinate bit has a value of 1; and
6) there are no more than 11 consecutive zeros in any sequence of one or more codewords, and there are no more than 7 consecutive alternating bits (every other bit) in the sequence that have a value of 0.
In a second embodiment of the rate 16/17 code, if a codeword Hxe2x80x3 is (H1xe2x80x3 H2xe2x80x3), where H1xe2x80x3 represents the first 11 bits of Hxe2x80x3, and H2xe2x80x3 represents the last 6 bits of Hxe2x80x3, then:
1) each codeword Hxe2x80x3 has at least 7 bits with a value of 1;
2) H1xe2x80x3 has at least 3 bits with a value of 1;
3) H2xe2x80x3 has at least 2 bits with a value of 1;
4) H2xe2x80x3 has at least 1 odd-coordinate bit with a value of 1, and at least 1 even-coordinate bit has a value of 1;
5) there are no more than 11 consecutive zeros in any sequence of one or more codewords, and there are no more than 10 consecutive alternating bits (every other bit) in the sequence that have a value of 0; and
6) Early Decoding Property (EDP)xe2x80x94H1xe2x80x3 may be used alone (without H2xe2x80x3) to recover from its codeword the first byte (8 bits) of un-encoded data corresponding to the codeword of H2xe2x80x3.
These, together with other aspects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.